Last year was the fourth warmest since record-keeping began in 1880, with a global average surface temperature about 1 degree Celsius above the pre-industrial era, climate scientists said on Wednesday.
The data also confirm that, taken as a whole, the years 2015-18 were warmer than any other four-year period on record, a trend that the scientists said was more important than ranking the individual years.
“The degree of warming during the past four years has been exceptional, both on land and in the ocean,” said Petteri Taalas, secretary general of the World Meteorological Organization (WMO) in Geneva.
The data show that the 20 warmest years on record have occurred in the past 22 years, the WMO said in a news release.
The WMO released the data simultaneously with the US space agency NASA and the National Oceanic and Atmospheric Administration (NOAA) in Washington.
The scientists stressed that the data, based on a consolidated analysis by the WMO of five international data sets, are a clear sign of continuing long-term climate change associated with record atmospheric concentrations of greenhouse gases.
“The key message is that the planet is warming. The long-term trends are extremely robust,” said Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies. “There is no question about those trends existing in the data no mater how we slice it.”
Schmidt and Derek Arndt, head of NOAA’s National Centers for Environmental Information, spoke with reporters on a conference call.
They noted that 2016 remains the warmest year on record, 2015 remains the second-warmest and 2017 the third, following a similar up-and-down pattern dating back to about 1960. Arndt likened the jagged nature of the temperature readings over the last several decades to a person moving up an escalator while jumping up and down.
The scientists also note that temperatures are only part of the story. Extreme weather events in 2018 affected many countries and millions of people, with devastating repercussions for economies and ecosystems.
Disasters in the US in 2018 cost 91 billion dollars in direct losses, the fourth-largest total on record, NASA and NOAA said. These included hurricanes Michael and Florence, costing about 25 billion dollars and 24 billion dollars, respectively, and western wildfires, costing about 24 billion dollars.
In addition, the United States had its third-wettest year in 2018, with record rainfall in parts of the eastern US, while the south-west region suffered from drought, the NASA and NOAA data show.
Schmidt said these weather-related events are consistent with the increase in average global temperature.
The WMO also commented on recent extreme weather, namely in Australia, where it’s currently summer.
The country experienced the warmest January since records began, while the island of Tasmania saw the driest January ever.
At the same time, the US, which is in winter, has experienced extreme cold, which Taalas said “certainly does not disprove climate change.”
The cold weather spell could be linked in part to dramatic changes in the Arctic, which is warming twice as fast as the rest of the world, he added. “What happens at the poles does not stay at the poles but influences weather and climate conditions in lower latitudes where hundreds of millions of people live,” he said.